Grinding machine

ABSTRACT

A grinding machine in which the abrasive wheel grinds not only a cylindrical surface, but also spaced radial surfaces of a workpiece, and in which a dressing apparatus is provided for dressing the end surfaces of the wheel.

United States Patent Robillard et al.

[ June 19, 1973 GRINDING MACHINE 1,936,731 11/1933 Perkins 125 11 ST3,098,328 7 1963 Fournier.... 51/165 R [751 Inventors- Edward Valley3,403,480 10 1968 Robillard 5l/165.87

Herbert R. Uhtenwoldt, Worcester, both of Mass. FOREIGN PATENTSORAPPLICATIONS [73] Assignee: Cincinnati Milacron-Heald Corp., 231,3305/1969 U.S.S.R 51/16587 Worcester, Mass.

[22] Filed: May 17, 1971 Primary Examiner-Harold D. Whitehead Att --N S.131 d tt 21 Appl. No.: 143,930 omey Oman ge 52 us. (:1 51/5, 51/165.87,51/327 ABSTRACT [51] Int. Cl B241) 5/06 [58] Field 61 Search 51 /165.87,165.88, A gmdmg 9? whch the abraswe wheel f not only a cylmdrlcalsurface, but also spaced radIal 51/165.91,165.93,165.78, 165, 5,327

surfaces of a workplece, and In WllllCl'l a dressmg appa- [56]References Cited $222118 pr0v1ded for dressmg the end surfaces of theUNITED STATES PATENTS 2,077,363 4/1937 Hulbert 125/11 ST 5 Claims, 3Drawing Figures TABLE \N ADI.

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WHEELWEAR coMPcuamwN oos'oecz\.emr\ou {r ACCELERA'HON GRINDING MACHINEBACKGROUND OF THE INVENTION In the art of finishing workpiece surfacesby the abrasive method, it is often desirable to grind not only alongitudinal or cylindrical surface of revolution on a workpiece, butalso certain generally radial surfaces. A workpiece in which thissituation exists would be repre sented by a roller bearing outer racewith a groove having a rectangular cross-section with a cylindricalsurface at the ends of which exists a purely radial surface. In thepast, these operations have been performed by so-called plunge grindingwherein the wheel has the exact shape of the groove and is movedradially directly into the roughly-formed groove for the finishingoperation. The difficulty with this method of approach to the problem isthat it is very difficult to dress the end surfaces of the wheel whichhave been dulled by the plunge-grinding without, at the same time,reducing the size of the groove, i.e., the distance between the twoparallel radial surfaces. Usually, the wheel has been dressed by using adiamond form dresser having the exact shape of the desired groove, butthe problem still exists that it is difficult, if not impossible, todress the end surfaces of the wheel without changing the dimensions ofthe groove. Attempts to overcome this difficulty have resulted in veryexpensive and delicate equipment which have not been wholly satisfactoryfrom the point of view of repeatability of dimension and other qualitiesof the finished workpiece. For instance, if one desires to dress the endsurfaces of a grinding wheel in the same way that is conventionallyperformed on the peripheral surface of the grinding wheel, compensationmust be made for the amount of abrasive wheel that has been removed. Ifthe wheel is not so dressed, not only does the quality of the finishedsurface suffer, but the grinding operation takes longer, which isunacceptable in the case of an expensive automatic grinding machine.These and other difficulties experienced with the prior art devices havebeen obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide agrinding machine including means for dressing the end surfaces of acylindrical abrasive wheel.

Another object of this invention is the provision of a grinding machinehaving means for reciprocating the grinding wheel in a groove havingsubstantial radial surfaces to grind these surfaces alternately at theends of the reciprocation.

.A further object of the present invention is the provision of agrinding machine making use of the end surface of the abrasive wheel,provision being made for dressing the ends and for compensating at thetime of dress for the removal of portion of the abrasive wheel.

It is another object of the instant invention to provide a grindingmachine for grinding grooves by reciproca tion instead of plunge, whichmachine is simple and inexpensive to manufacture and which is capable ofa long life of useful service with a minimum of maintenance.

With these and other objects in view, as will be apparent to thoseskilled in the art, the invention resides in the combination of partsset forth in the specification and covered by the claims appendedhereto.

SUMMARY OF THE INVENTION In general, the invention consists of agrinding machine for generating a surface of revolution on a workpiecehaving a base, a workhead table mounted on the base and having a holderto support the workpiece, and a wheelhead table mounted on the base andhaving a rotatable spindle for carrying an abrasive wheel. Feed means isprovided for bringing about relative movement transversely of the axisof the surface of revolution between the tables to bring a cylindricalsurface of revolution between the tables to bring a cylindrical surfaceof the wheel into grinding contact with the work piece. A dressingapparatus is provided including two spaced facing diamonds for dressingthe end surfaces of the wheel. Traverse means is provided for bringingabout relative movement longitudinally of the axis in cluding a means toplace the wheel in a first position generally co-extensive with the saidsurface of the workpiece and means to place the wheel in a secondposition co-extensive with the said dressing apparatus.

A means is provided which is operative to reciprocate the wheel on afirst stroke to bring one end surface into grinding contact with aradial portion of the workpiece surface and then to bring the other endsurface into grinding contact with another radial portion of theworkpiece surface.

Another means is provided which is operative to move the wheel on asecond stroke to bring the said one end surface of the wheel intodressing contact with one of the diamonds and then to move the saidother end surface of the wheel into dressing contact with the other ofthe diamonds.

More specifically, a control is connected to the first and second meansto lengthen the second stroke at the time of every dressing operationand to lengthen the first stroke by a commensurate amount.

BRIEF DESCRIPTION OF THE DRAWINGS The character of the invention,however, may be best understood by reference to one of its structuralforms, as illustrated by the accompanying drawings, in which:

FIG. 1 is a plan view of a grinding machine embodying the principles ofthe present invention,

FIG. 2 is an electrical schematic diagram showing the controls for astepping motor forming part of the invention, and

FIG. 3 is a diagrammatic view showing the manner in which the abrasivewheel is reciprocated within a groove in a workpiece.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1,wherein are best shown the general features of the invention, thegrinding machine, indicated generally by the reference numeral 10, isshown as having a base 11 on which is mounted a workhead table 12 and awheelhead table 13. The workhead table 12 is mounted on ways 14 forsliding motion longitudinally under the impetus of an hydraulic cylinder15. Similarly, the wheelhead table 13 is mounted on ways 16 fortransverse motion under the influence of a hydraulic cylinder 17.Mounted on the wheelhead table is a wheelhead 18 in which is rotatablymounted a spindie 19 on the outer end of which is mounted an abrasivewheel 21. This wheel is of the usualcylindrical type having acylindrical peripheral surface 22 and two radial end surfaces 23 and 24.

Mounted on the workhead table 12 is an upper table 25 which is mountedon ways 26 for longitudinal motion over the top of the table 12 underthe impetus of a hydraulic cylinder 27. Mounted on the upper surface ofthe table 25 is a workhead 28 suitably constructed to support and rotatea workpiece 29 which has a groove 31 which is to be finished by theabrasive process.

Also mounted on the upper table 25 is a dresser 32 for dressing thecylindrical surface of the abrasive wheel 21 and a dresser 33 fordressing the end surfaces 23 and 24. The dresser 33 is provided with aswingable element 34 which is hinged on a longitudinal pivot shaft 35.The element has two parallel spaced arms 36 and 37 having parallelfacing surfaces from which extend facing diamonds. The dresser 33 isprovided with a pneumatic cylinder 49 which serves to swing the element34 about its axis.

The underside of the table 12 is provided with a recess 38 in which liesa compensating slide 39 which is slidably carried on the upper surfaceof the table 12. The slide 39 is moved longitudinally by means of a ballscrew 41 operated through a gear train 42 by a stepping motor 43. Theslide 39 is provided with a finger 44 having oppositelongitudinally-directed faces provided with hardened metal buttons 45and 46. The button 46 is arranged to contact a button 47 mounted on avertical surface of the table 25, while the button 45 is arranged tocontact an adjustable stop 48 which faces the surface with the button47.

Referring now to FIG. 2, it can be seen that the motor 43 receivespulses from a driver 51 which, in turn, receives its signal from apulse-to-step converter 52. The logic circuit 53 is connected by a line54 to a pulser 55 having acceleration and deceleration functions. A line56 joins the output of the pulser 55 with the pulse-tostep converter 52.The logic circuit is also connected by a line 57 to a sequencing circuit58. The circuit 58 is connected to the converter 52 by lines 59 and 61,and by lines 62 and 63 to a counter 64..

The logic circuit 53 is also connected to the counter 64 by a line 65,while the line 56 is also connected to the counter by a line 66. Alsoassociated with the apparatus is a counter 67 which is provided with amechanical memory and a circuit 68 containing compensation, dock, andcounting circuits. The three lines 69, 70, and 71 join the counter 67 tothe circuit 68. The three lines 72, 73, and 74 join the counter 67 to awheel wear counter 75, and line 76 joins the counter 75 to the line 66and to the line 56, as well as to a line 77 connected to a reversalcounter 78. A line 79 joins the logic circuit 53 t the counter 78, whilethe line 81 joins the circuit 53 to the counter 75.

The operation of the invention will now be readily understood in view ofthe above description. The grinding machine is used in a conventionalgrinding cycle involving longitudinal movement between the wheelhead andthe workpiece 29, as well as transverse movement for feeding. Thelongitudinal movement takes place under the impetus of the cylinderwhich serves to move the table 12 and, therefore, the workpiece 29 tothe position in which the wheel 21 lies within the workpiece 29. Thehydraulic cylinder 27 serves to move the upper table 25 relative to thelower table 12 and, therefore, relative to the wheelhead 18 in order tobring the dressers 32 and 33 sequentially into operative relationship tothe wheel 21. Normally, the dresser 33 would operate on the wheel 21 asit moves longitudinally from the first position within the workpiece 29to a second position coextensive with the dresser 33. Once the wheel 21lies either within the workpiece 29 or the coextensive with the dresser33, it is moved longitudinally small amounts by the stepping motor 43cooperating with the stop 47 and with the stop 48. The stroke that isused within the workpiece 29 is the same as the stroke used between thediamonds and the dresser 33. During these strokes, the stop 43 on thetable 25 is maintained in a position pressed against the button 46 onthe finger 44 of the compensation slide 39. The stroke takes place byintroducing pulses of the proper mode into the stepping motor 43 so thatthe compensation slide 39 moves back and forth and the table 25,therefore, moves with it; the workpiece 29, of course, then moves backand forth over the wheel 21 to produce the grinding operation. In thesame way, the dresser 33 moves relative to the wheel 21 to bring it intoposition to allow the proper dressing operation on the ends of thewheel.

ln FIG. 3, it can be seen that the groove 31 in the workpiece 29 isgenerally rectangular in cross-section and, therefore, is provided witha cylindrical surface 82 and two opposed, facing, radial surfaces 83 and84. The workpiece 29 is moved longitudinally to bring the end surface 23of the wheel 21 into contact with the radial surface 84 of the grooveand, then, at the other end of the stroke, the end surface 24 of thewheel comes in contact with the radial surface 83 of the workpiece. Atthe same time, the wheelhead is moved by the cylinder 17 into contactwith the cylindrical surface 82 and produces a finish grind on thatsurface also. The cross-feed takes place in the conventional manner andthere is no necessity for describing it in detail. The reciprocatingmovement, however, of the workpiece relative to the wheel is shown indetail in FIG. 3. Because of the fact that the motion takes place underthe control of the stepping motor 43 and the stepping motor rotates andfeeds the workpiece relative to the abrasive wheel in accordance withthe number of pulses, introduced into the motor, their rate ofintroduction, and so on, it can be seen that it is a very easy matter togive this motion exactly the desired one, including the desireddeceleration and acceleration at the ends of the stroke. It can be seenthat each movement of the wheel on each side of the centerline consistsof an initial setting that was used with the new wheel during setup plusan additional amount equal to wheel wear compensation that is introducedat the time of each dressing operation on the dresser 33.

When the wheel is moved out to be operated on by the dresser 33, thetable is pressed by the cylinder, so that the button 47 contacts thebutton 46 on the compensation slide and the motion to bring. the ends ofthe wheel into contact with the diamonds takes place on either side ofthis position as a centerline. In a similar manner, when the wheel 21lies in the workpiece 29, the stop 48 is used as such a centerline andis adjusted during setup for that particular position. Returning to thecondition where the wheel lies between the arms 36 and 37 of the dresser33, the dresser is in raised posi tion until the wheel has beenpositioned at one end or the other of the stroke. Then, the cylinder 49is actuated to swing one of the arms with its diamond downwardly, thediamond contacting the wheel and dressing its end surface. The positionis reversed to dress the other end of the wheel. The wheel is thenreturned to the workpiece which, in some grinding cycles, may be a newworkpiece. In any case, the cycle is continued from one workpiece toanother. It can be seen, then, that the production of accurately groundworkpieces of this type can take place by means of relatively simpleapparatus and that the machine automatically compensates for the amountof the abrasive wheel that is re moved during the dressing operation.

It is obvious that minor changes may be made in the form andconstruction of the invention without departing from the material spiritthereof. It is not, however, desired to confine the invention to theexact form herein shown and described, but it is desired to include allsuch as properly come within the scope claimed.

The invention having been thus described, what is claimed as new anddesired to secure by Letters Patent 1. A grinding machine for generatinga surface of revolution on a workpiece, comprising a. a base,

b. a workhead table mounted on the base and having a holder to supportthe workpiece, c. a wheelhead table mounted on the base and having arotatable spindle for carrying an abrasive wheel,

(1. feed means for bringing about relative movement transversely of theaxis of the surface of revolution between the tables to bring acylindrical surface of the wheel into grinding contact with theworkpiece, a dressing apparatus including two spaced facing diamonds fordressing the end surfaces of the wheel,

f. traverse means for bringing about relative movement longitudinally ofthe axis, including a first means to place the wheel in a first positiongenerally co-extensive with the said surface of the workpiece and asecond means to place the wheel in a second position generallyco-extensive with the said dressing apparatus, the first means beingoperative to reciprocate the wheel on a first stroke to bring one endsurface into grinding contact with a radial portion of the workpiecesurface and then to bring the other end surface into grinding contactwith another radial portion of the workpiece surface, the second meansbeing operative to move the wheel on a second stroke to bring the saidone end surface of the wheel into dressing contact with one of thediamonds and then to move the said other end surface of the wheel intodressing contact with the other of the diamonds.

2. A grinding machine as recited in claim 1, where a control isconnected to the first and second means to lengthen the second stroke atthe time of every dressing operation and to lengthen the first stroke bya commensurate amount.

3. A grinding machine as recited in claim 1, wherein the dressingapparatus includes a pair of longitudinally spaced arms swingablymounted on a common longitudinal axis, the arms being facing surfaces onwhich the two diamonds are mounted.

4. A grinding machine as recited in claim 1, wherein the traverse meansincludes a cylinder for producing the longitudinal movement to the firstposition and the second position and stepping motor for producing thefirst and second strokes.

5. A grinding machine as recited in claim 4, wherein the workhead tableis provided with a first stop to 10- cate the abrasive wheel in theworkpiece at the center of the first stroke and with a second stop tolocate the one side and the other of the centers of the strokes.

1. A grinding machine for generating a surface of revolution on aworkpiece, comprising a. a base, b. a workhead table mounted on the baseand having a holder to support the workpiece, c. a wheelhead tablemounted on the base and having a rotatable spindle for carrying anabrasive wheel, d. feed means for bringing about relative movementtransversely of the axis of the surface of revolution between the tablesto bring a cylindrical surface of the wheel into grinding contact withthe workpiece, e. a dressing apparatus including two spaced facingdiamonds for dressing the end surfaces of the wheel, f. traverse meansfor bringing about relatiVe movement longitudinally of the axis,including a first means to place the wheel in a first position generallyco-extensive with the said surface of the workpiece and a second meansto place the wheel in a second position generally co-extensive with thesaid dressing apparatus, the first means being operative to reciprocatethe wheel on a first stroke to bring one end surface into grindingcontact with a radial portion of the workpiece surface and then to bringthe other end surface into grinding contact with another radial portionof the workpiece surface, the second means being operative to move thewheel on a second stroke to bring the said one end surface of the wheelinto dressing contact with one of the diamonds and then to move the saidother end surface of the wheel into dressing contact with the other ofthe diamonds.
 2. A grinding machine as recited in claim 1, where acontrol is connected to the first and second means to lengthen thesecond stroke at the time of every dressing operation and to lengthenthe first stroke by a commensurate amount.
 3. A grinding machine asrecited in claim 1, wherein the dressing apparatus includes a pair oflongitudinally-spaced arms swingably mounted on a common longitudinalaxis, the arms being facing surfaces on which the two diamonds aremounted.
 4. A grinding machine as recited in claim 1, wherein thetraverse means includes a cylinder for producing the longitudinalmovement to the first position and the second position and steppingmotor for producing the first and second strokes.
 5. A grinding machineas recited in claim 4, wherein the workhead table is provided with afirst stop to locate the abrasive wheel in the workpiece at the centerof the first stroke and with a second stop to locate the abrasive wheeladjacent the dressing apparatus at the center of the second stroke, andwherein a compensation slide is located between the two stops and isdrivingly connected to the stepping motor, so that the introduction ofpulses to the stepping motor serves to move the workhead table andworkpiece alternately to one side and the other of the centers of thestrokes.